This invention relates to an implantable infusate pump. It relates more particularly to an implantable pump having an inlet septum situated close to the patient's skin so that the pump can be refilled and recharged percutaneously.
Advances have been made in recent years in the design and development of mechanical devices for implementation in the human body. These include heart valves, heart stimulators and small external pumps for infusion of medicine to various sites in a person's body. The obvious advantage of implanting devices such as these is that there is no permanent opening through the patient's skin which could be a site of infection.
Implantable pumps were envisioned some years ago. Recently, one such pump has been developed which is particularly effective. That pump is described in U.S. Pat. No. 3,731,681, dated May 8, 1973 entitled IMPLANTABLE INFUSION PUMP. The present invention is an improvement on that pump.
One problem encountered with the prior pump is that minute amounts of hair and skin sometimes enter the pump chamber and clog the outlet tube leading to the infusion site in the body. Such obstructions slow the flow of infusate to the site and sometimes interrupt flow entirely. Apparently this foreign matter is introduced into the pump chamber when infusate is being injected through the penetrable septum to refill and recharge the pump. Such blockage could, of course, present serious problems for the patient and, at the very least, it would necessitate an operation to remove and replace the pump. Proposals to avoid this problem by placing a filter between the pump chamber and the outlet tube have not been entirely satisfactory because the debris tends to accumulate on the filter and still reduce the flow of infusate to the infusion site.
The prior implantable pump is also somewhat disadvantaged because it is not compatible enough with the human body. This is due to a variety of factors. The pump is relatively large and bulky and, therefore, requires a relatively large space in the body. Also, it contains various exterior promentories and recesses where body fluids accumulate after implantation and may become infected, resulting in a requirement for treatment or possibly pump removal. Furthermore, the pump's outlet tube does not control the flow of infusate accurately enough at the very low flow rates involved. Finally, that pump employs several turned and threaded fittings requiring gaskets, making it relatively expensive to make and prone to leakage of infusate liquid and the vapor used as a pressure source.